Is there a clever way of inserting a file or folder into ...
 

a bin/cue or ISO image without extracting and dumping the content of the cd onto the HDD first?

Also, why do people have to convert a bin/cue image to an ISO image before extracting its content onto a HDD or burning it as an ISO image?

1. No there isn't.
2. They don't, they do it because they are stupid.